www/py-dj51-social-auth-app-django: Update to 5.6.0

Changelog:

https://github.com/python-social-auth/social-app-django/releases/tag/5.6.0

MFH: 2025Q4
Security: 3116b6f3-b433-11f0-82ac-901b0edee044
(cherry picked from commit 821abd3d6f1cf1ab1a9aaedab42da09ed27e74d5)